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82 lines
2.5 KiB
C
82 lines
2.5 KiB
C
/* Copyright (C) 2021 fef <owo@fef.moe>. All rights reserved. */
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#pragma once
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#include <arch/page.h>
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#include <gay/cdefs.h>
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#include <gay/systm.h>
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#include <gay/types.h>
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/**
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* @brief Stores information about a single page in physical memory.
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* There is exactly one of these for every physical page, no matter what that
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* page is used for or whether it is usable at all.
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*/
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struct vm_page {
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/** @brief Reference count (0 = unused) */
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atom_t count;
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/** @brief Various flags describing how and for what the page is used, see below */
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u_int flags;
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/** @brief Singly linked list, if the page is free */
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patom_t next;
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/**
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* @brief Request this page to be freed if possible.
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* This callback may be `nil` unless the `PG_FREEABLE` bit in `flags`
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* is set. The presence of this bit does *not* guarantee that the page
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* is actually reclaimable, it's merely a performance optimization to
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* avoid having to call this function on pages that can never be
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* reclaimed anyway.
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*
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* @param page Pointer to the page itself
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* @return 0 if the page could be reclaimed and is now free
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*/
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int (*try_free)(struct vm_page *page);
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/**
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* @brief Optional extra data pointer, reserved for private use.
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* The current owner of the page may use this to track the underlying
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* object in memory (or pretty much anything else), for example the
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* `struct slab` if this page is currently used by the slab allocator.
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* Useful for implementing the `try_free()` callback.
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*/
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void *extra;
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};
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typedef struct vm_page *vm_page_t;
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/* values for struct page::flags */
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/** @brief Page must never be accessed */
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#define PG_RESERVED (1 << 0)
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/** @brief Page is in an atomic per-cpu cache */
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#define PG_ATOMIC (1 << 1)
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/** @brief Page is used by the slab allocator */
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#define PG_SLAB (1 << 2)
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/** @brief It **might** be possible to reclaim this page using `try_free()` */
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#define PG_FREEABLE (1 << 3)
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/** @brief Array of every single page in physical memory, indexed by page frame number. */
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extern struct vm_page *const vm_page_array;
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#ifdef DEBUG
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extern vm_page_t _vm_page_array_end;
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#endif
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/** @brief Get the page frame number of a page. */
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__pure2 static inline u_long pg2pfn(vm_page_t page)
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{
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KASSERT(page < _vm_page_array_end);
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return page - vm_page_array;
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}
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__pure2 static inline u_long paddr2pfn(vm_paddr_t paddr)
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{
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KASSERT(&vm_page_array[paddr >> PAGE_SHIFT] < _vm_page_array_end);
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return paddr >> PAGE_SHIFT;
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}
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__pure2 static inline vm_page_t paddr2pg(vm_paddr_t paddr)
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{
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vm_page_t page = vm_page_array + (paddr >> PAGE_SHIFT);
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KASSERT(page < _vm_page_array_end);
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return page;
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}
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